Copper alloy sheet

Abstract

The present invention relates to a Cu—Ni—Sn—P-based copper alloy sheet having a specific composition, where (1) the copper alloy sheet is set to have an electrical conductivity of 32% IACS or more, a stress relaxation ratio in the direction parallel to the rolling direction of 15% or less, a 0.2%-proof stress of 500 MPa or more and an elongation of 10% or more; (2) the X-ray diffraction intensity ratio I(200) / I(220) in the sheet surface is set to be a given value or less and at the same time, anisotropy in the stress relaxation resistance characteristic is reduced by fining the grain size; (3) the texture of the copper alloy sheet is set to a texture such that the distribution density of B orientation and the sum of distribution densities of B orientation, S orientation and Cu orientation each is set to fall in a specific range and bendability is thereby enhanced; or (4) the dislocation density measured using the value obtained by dividing the half-value breadth of the X-ray diffraction intensity peak from {200} plane in the copper alloy sheet surface by the peak height is set to a given value or more and press punchability is thereby enhanced. The Cu—Ni—Sn—P-based copper alloy sheet of the present invention is excellent in the properties required for a terminal or connector and further (1) has excellent strength-ductility balance, (2) satisfies the stress relaxation resistance characteristic in the direction orthogonal to the rolling direction, (3) has excellent bendability, or (4) has excellent press punchability.

Description

TECHNICAL FIELD[0001]The present invention relates to a copper alloy sheet. More specifically, the present invention relates to a copper alloy sheet having properties suitable for a connection component such as automotive terminal or connector.BACKGROUND ART[0002]A connection component such as automotive terminal or connector recently requires a performance enough to ensure reliability in a high-temperature environment such as engine room. One of most important properties for the reliability in a high-temperature environment is a contact-fitting force maintaining characteristic, that is, a stress relaxation resistance characteristic.[0003]FIG. 4 shows a structure of a box-type connector (female terminal 3) representative of a connection component such as automotive terminal or connector. FIG. 4(a) is an elevational view and FIG. 4(b) is a cross-sectional view. In FIG. 4, the female terminal 3 has a pressing strip 5 cantilever-supported in an upper holder part 4 and when a male termi...

AI Technical Summary

Benefits of technology

[0044]The present inventors have succeeded in obtaining a copper alloy sheet with excellent strength-ductility balance according to the first embodiment of the present invention by the above-described characteristic control of finish annealing conditions, where the electrical conductivity is enhanced more than the usually expected effect of elevating the electrical conductivity without reducing the strength which usually decreases by the finish annealing and the elongation of the obtained copper alloy sheet is enhanced while maintaining the stress relaxation resistance characteristic. From a commonsense standpoint, the strength after finish annealing usually decreases due to a recovery / recrystallization phenomenon during finish annealing. Nevertheless, under the above-described characteristic control of finish annealing conditions, surprisingly, the strength is not reduced but is maintained and the elongation is rather enhanced. The electrical conductivity is also elevated.

[0045]Namely, in the conventional Cu—Ni—Sn—P-based alloy sheet, the elongation is less than 10% despite a 0.2%-proof stress of 500 MPa or more, and the electrical conductivity is less than 35% IACS despite a stress relaxation ratio of 15% or less. On the other hand, according to the first embodiment of the present invention, a novel Cu—Ni—Sn—P-based alloy sheet having, even when the 0.2%-proof stress is 500 MPa or more, an elongation of 10% or more, an electrical conductivity of 32% IACS or more and a stress relaxation ratio of 15% or less is obtained. More excellent properties of this Cu—Ni—Sn—P-based alloy sheet are such that the electrical conductivity is 35% IACS or more, the stress relaxation ratio is 15% or less in the direction parallel to the rolling direction, the 0.2%-proof stress is 520 MPa or more, and the elongation is 12% or more.

[0046]This copper alloy sheet with excellent strength-ductility balance according to the first embodiment of the present invention was subjected to systematic analysis and analyzed in detail for the grain shape, analyzable fine crystallized product such as Ni—P compound, the oxide and the like, but to date, a systematic clear distinction in terms of the structure cannot be drawn between the conventional copper alloy sheet and the present invention. The systematic analysis instruments used herein are SEM (scanning electron microscope), TEM (transmission electron microscope) and the like, which are generally used for direct systematic analysis of this type. Of course, the copper alloy sheet compositions investigated are utterly the same Cu—Ni—Sn—P-based alloy and the production conditions are the same conditions except for changing the finish annealing conditions among samples.

[0047]Therefore, the present inventors further performed, as the systematic analysis, X-ray diffraction which is special as compared with the direct systematic analysis means, that is, SEM and TEM. As a result, it has been found that, as described later, in the copper alloy sheet with excellent strength-ductility balance according to the first embodiment of the present invention, an intensity peak is present at the X-ray diffraction angle (2θ) between 100° and 102° in the X-ray diffraction pattern, whereas in the conventional Cu—Ni—Sn—P-based alloy sheet, such an intensity peak is not present.

[0048]In other words, the present inventors have found that when such an intensity peak is present in a Cu—Ni—Sn—P-based alloy sheet, even with a 0.2%-proof stress of 500 MPa or more, the elongation is 10% or more, the electrical conductivity is 32% IACS or more, and the stress relaxation ratio is 15% or less. The present inventors have also found that when such an intensity peak is not present, like the conventional Cu—Ni—Sn—P-based alloy sheet, the elongation is less than 10% despite a 0.2%-proof stress of 500 MPa or more and the electrical conductivity is less than 32% IACS despite a stress relaxation ratio of 15% or less. That is, in fact, whether or not the alloy sheet is a novel Cu—Ni—Sn—P-based alloy sheet satisfying all of 0.2%-proof stress, elongation, electrical conductivity and stress relaxation resistance characteristic is depending on whether the above-described specific intensity peak is present or not.

[0049]The presence of the specific intensity peak, namely, the specific intensity peak at the X-ray diffraction angle (2θ) between 100° and 102°, means that a certain compound is present in the copper alloy sheet texture. The present inventors anticipate that, as described later, this compound is a specific Sn-based compound. However, also as described later, despite various analyses on the relationship between the possible intermetallic compound in this alloy system and the intensity peak position in the X-ray diffraction pattern, what intermetallic compound assumes the above-described specific intensity peak is not clearly known and at present, the anticipation above is only a matter of speculation. Accordingly, how or whether the specific intensity peak contributes to the above-described difference or enhancement in terms of the properties of the Cu—Ni—Sn—P-based alloy sheet is not necessarily clarified.

Problems solved by technology

Accordingly, the stress relaxation resistance characteristic is such a resistance characteristic against high temperatures as not allowing great reduction in the contact-fitting force of the spring-shaped component composed of a copper alloy sheet even when the connection component is kept standing in a high-temperature environment.

This Cu—Ni—Sn—P-based alloy allows for ingot making in a shaft furnace which is a large-scale melting furnace with the opening being widely opened to the atmosphere, and because of its high productivity, a great cost down can be achieved.

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